高寒地区低能耗民居建筑DeST模拟

高寒地区建筑能耗消耗较大,为改进民居建筑结构保温性能,使用DeST软件进行高寒地区低能耗民居建筑模拟,运用三维激光扫描中的脉冲式测距方法采集民居建筑数据,应用滤波去噪方法处理点云数据,构建三角网模型,在特征线提取基础上建立高寒地区民居建筑三维模型;将空调系统、通风条件和典型日三类参数作为实验数据,利用DeST模拟民居建筑不同围护结构条件下冷热负荷情况,得到外墙、外窗、屋面因素对建筑的能耗影响规律.实验结果表明,节能工作中需着重提升外墙保温层厚度,最大限度减少窗墙比大小,严格控制屋面传热系数值,在提升高寒地区民居建筑节能效果同时,也为改进建筑围护结构保温性能提供可靠的现实依据.     

利用MATLAB编程计算精馏塔的热损失速率

根据对流传热的基本规律和精馏塔传热的特点,建立了精馏塔热损失的数学模型并推导了热损失速率的计算公式,随后采用MATLAB对精馏塔的热损失速率进行了编程计算;利用MATLAB图形用户界面(GUI)工具创建了计算程序的输入输出界面。利用所编写的计算程序和所创建的用户图形界面研究了精馏塔保温层厚度,空气温度、相对湿度和风速对精馏塔热损失的影响。结果发现随着保温层厚度的增加,精馏塔热损失速率迅速下降,但下降的速度越来越慢,在精馏塔热损失速率与保温层厚度关系曲线上存在一个拐点,该点可作为精馏塔外壁保温层厚度的最优值;风速和空气温度对精馏塔热损失速率也有一定的影响,随着风速的增大,精馏塔热损失速率迅速上升,但上升的速度越来越慢,最终趋近于一个恒定值;空气温度升高,精馏塔热损失速率下降,二者呈现出良好的线性关系;空气湿度对精馏塔热损失速率的影响不大,可以忽略不计。另外在计算过程中发现对精馏塔进行分段计算非常必要,不进行分段计算得到的结果只有分段计算结果的1/7左右,严重偏离真实值。     

蒸汽管网运行评价技术及应用

深入分析蒸汽在管网输送过程中的能量损失特征,将功损失、热损失加以区分,在此基础上构建能耗损失的计算模型,获得蒸汽管网经济流速并分析温度、压力、保温层厚度等不同因素下蒸汽管道能耗损失及经济流速的变化规律,为蒸汽管网运行评价与优化改造提供依据,并结合实际案例介绍运行评价技术的应用效果。结果表明:蒸汽散热损失受蒸汽流速、保温层厚度双重因素影响;蒸汽管网的经济流随着蒸汽操作压力的提高而降低、随着蒸汽温度的升高而增大;在相同操作流速下蒸汽温度越高能量损失越大、蒸汽压力越低能量损失越大。工程应用表明,在蒸汽管网运行评价的基础上进行蒸汽管网结构或操作优化,可有效降低输送环节的能量损失,获得显著的经济效益。     

基于BIM技术的被动式建筑节能因子多目标优化研究

为了研究被动式建筑节能策略,在原有的 BIM 模型基础上生成建筑能耗模型,通过 gbXML 数 据标准进行数据共享,在 Grasshopper 平台导入参数化建筑性能模拟模型,对目标建筑外表面进行太阳辐射分 析,确定以西面遮阳板倾斜角和深度、南面和西面窗墙比、外墙保温板厚度为被动式节能技术变量指标。利用 OpenStudio 进行建筑能耗分析,Daysim 进行全年动态自然采光模拟分析,以空间日光自主评价指标 sDA300/50%、 全年制冷、供暖能耗为相互制衡的适应度目标函数。最后使用 NSGA-Ⅱ算法进行多目标优化,得出帕累托前 沿解集。研究表明：寒冷 B 区,固定遮阳无法平衡制冷和供暖能耗目标。窗墙比仅通过制冷、供暖能耗目标无 法进行优化设计,应结合自然采光性能进行制衡。同时增加保温层厚度,提升外墙保温效果。BIM 模型提供了 建筑性能模拟数据来源,Grasshopper 平台结合模拟引擎和优化算法进行耦合分析,为被动式节能因子指标最 优值的搜索带来新的思路。     

典型关键层结构下覆岩采动应力分布规律研究

针对目前对煤层支承压力的研究大多基于工作面上覆岩层结构均化处理展开,未充分考虑其内在结构影响的问题,基于岩层控制关键层理论,通过改变关键层位置、厚度等,对典型关键层结构下覆岩采动应力分布规律进行了数值模拟研究。研究结果表明:随着关键层与煤层间距增大,工作面超前支承压力峰值逐渐减小,关键层下方软岩层超前支承压力峰值先减小后趋于稳定,关键层上方软岩层超前支承压力峰值先增大后趋于稳定,应力集中区域范围减小;随着关键层厚度增大,工作面超前支承压力峰值先增大后趋于稳定,上覆岩层超前支承压力峰值逐渐增大,应力集中区域范围增大。     

气化炉与辐射废锅接口托架传热的数值分析

以通用的三维导热模型为基础,应用有限元法,计算了不同结构参数和操作条件下气化炉与辐射废锅接口内金属托架的传热特性.结果表明,托架长度、耐火纤维厚度、炉内温度是影响托架温度和热流密度分布的主要因素.托架最高温度和最大热流密度随着托架长度的增加而增大,随着炉内温度的提高而增大.托架外围包裹20 mm厚的耐火纤维,能有效降低托 .架的最高温度和最大热流密度.对于稳态操作的气化炉,其炉内温度变化范围约1 200℃～1 400℃,相应的金属托架最高温度变化范围约为420℃～480℃,最大热流密度约为(42.8～50.0)kW·m-2.     

基于LabVIEW的机械密封端面真实接触面积数值模拟

机械密封端面的真实接触面积对端面间的摩擦磨损特性和密封性能有着重要的影响;依据分形理论,考虑摩擦作用的影响,建立了机械密封端面无量纲真实接触面积的计算模型;基于LabVIEW编制了机械密封端面真实接触面积数值模拟程序,通过数值模拟计算得到了NHM70型机械密封端面间的无量纲真实接触面积Ar与端面比载荷Pg、端面分形维数D及特征尺度系数G的关系曲线;研究表明,真实接触面积随着端面比载荷的增大而单调地非线性增大;随着特征尺度系数的增大先急剧减小,而后缓慢减小;随着分形维数的增大先增大,后减小,即存在一最佳分形维数,使密封端面间的真实接触面积最大.     

一种基于能耗度量的融合树构建算法

基于传感器节点能耗情况对数据压缩以及数据融合进行了分析,针对在非完全融合情况下,贪婪增长树(GIT)算法构建融合树时并不能很好选择最优路由的问题,提出了一种基于能耗度量的融合树构建算法,通过融合节点反馈能耗以及到达Sink节点的跳数信息,对多个路由的能耗进行评估,进而选择低能耗路由.同时提出了一种由信息源节点进行路径加强的策略,减小了路径加强信息量以及多路径记录带来的负担.模拟实验数据表明,该算法在数据融合压缩比较小的情况下节能效果优于贪婪增长树GIT算法,并且随着信息源与Sink节点距离的增大,路径加强信息的数量也有很大降低.     

粉煤灰传热的影响研究

近年来国内外竞相开展利用粉煤灰等制备保温材料的研发工作,以粉煤灰传热为研究对象,对粉煤灰内的流场、温度场、高温壁面平均努谢尔数Nu进行研究;采用整场求解法方法进行数值求解,对网格的独立性和计算过程进行了验证;得到了粉煤灰传热一些基本数据,分析了粉煤灰温度场和流场随瑞利数Ra的变化规律。研究结果表明:随着Ra增加,开始流线均匀分布为一个顺时针大窝,逐渐变化为流线集中分布在流场外侧,而在中央基本上保持静止状态;当Ra很小时,无量纲等值线近似于平行高低温壁面的垂直线,随着Ra数逐渐增大,对应的温度等值线近似呈高温至低温的线性变化趋势;Ra小于10~5时,高温壁面Nu基本为2.37～3.31的定值;高温壁面底部努谢尔数Nu数大,最大值为30.8,上部Nu数小,最小值为1.19。     

非均匀内热源对多孔介质内复合对流传热传质的数值研究

采用数值方法分析了具有非均匀内热源的竖直套管中复合对流传热传质,考查内热源分布系数M和热质二浮力比N对速度、温度、浓度分布以及Nusselt数和Sherwood数的影响,讨论了Da数对复合对流传热传质的影响.结果表明:当N＞1时速度V为正,其值随N的增加而增大:当N＜-1.5时,V则先负后正.随着M增大,内外壁面处流线...     

肋板结构外保温设计方法

为合理设计肋板外保温结构2层保温材料的厚度,采用稳态热平衡理论计算初步确定厚度方案,采用Abaqus软件对外保温结构进行仿真分析,结果认为规则部位内保温层与外保温层之间的界面温度满足工程要求,验证理论计算的合理性.保温层圆角过渡部位内保温层与外保温层之间界面温度不满足设计要求,采用Abaqus优化模块对局部尺寸进行优化计算,确定该部位2层保温材料的厚度分布,得到满足设计要求的外保温层厚度组合.根据优化方案制作试件并进行试验测试,结果满足工程应用要求.     

Managing heat rejected from air conditioning systems to save energy and improve the microclimates of residential buildings

Simulations are conducted to investigate the influence and improvement potential of air conditioning heat rejection management of residential buildings on microclimate and energy use. The microclimate and building energy use are simulated on a typical high-rise building in Taipei, Taiwan, on a summer night. Heat rejection from the air conditioners is estimated with a building energy program, EnergyPlus, and a computational fluid dynamics (CFD) program, Windperfect, is used to analyze how heat rejection affects the outside thermal environment. Results show that heat rejection from air conditioners worsens the thermal environment below the urban canopy, thus increasing building energy use. Three countermeasure cases of heat rejection management, which consider the type of cooling system and its installation position, are proposed in this study. The average air temperature increase around the buildings caused by heat rejection was analyzed by transferring the simulation results of the building energy program to the CFD model on an hourly basis. Results show that the air temperature next to the building envelope and the air temperature around air conditioners decrease and that there is a reduction in electricity consumption by the air conditioners when a split-type air conditioner is installed on each floor or on every third floor. A reduction in the ambient air temperature below the urban canopy can be obtained by placing a cooling tower on the roof of the building.     

Optimal structure for heat and cold protection under transient heat conduction

A suitable combination of materials for sheltering a system from a sudden change of environmental temperature has been theoretically studied. The protective composite wall consists of two materials. An insulating material is placed on the outer surface, while, for the inner surface, materials that have good heat storage properties but negligible heat transfer resistance are chosen. The results show that by replacing some of the insulation material with a heat storage material, the temperature of the protected system can be maintained at a considerably lower level. Although the optimal thickness ratio X depends on the Biot number, Fourier number, and on the heat capacity ratio K _C, for a large number of thermal protection cases, the approximation X = 0.45 yields practically the minimum progress of the transient. If the Biot number is sufficiently small, it is better to replace all of the insulation material with a good heat storage material.     

An automated vision-based method for rapid 3D energy performance modeling of existing buildings using thermal and digital imagery

Modeling the energy performance of existing buildings enables quick identification and reporting of potential areas for building retrofit. However, current modeling practices of using energy simulation tools do not model the energy performance of buildings at their element level. As a result, potential retrofit candidates caused by construction defects and degradations are not represented. Furthermore, due to manual modeling and calibration processes, their application is often time-consuming. Current application of 2D thermography for building diagnostics is also facing several challenges due to a large number of unordered and non-geo-tagged images. To address these limitations, this paper presents a new computer vision-based method for automated 3D energy performance modeling of existing buildings using thermal and digital imagery captured by a single thermal camera. First, using a new image-based 3D reconstruction pipeline which consists of Graphic Processing Unit (GPU)-based Structure-from-Motion (SfM) and Multi-View Stereo (MVS) algorithms, the geometrical conditions of an existing building is reconstructed in 3D. Next, a 3D thermal point cloud model of the building is generated by using a new 3D thermal modeling algorithm. This algorithm involves a one-time thermal camera calibration, deriving the relative transformation by forming the Epipolar geometry between thermal and digital images, and the MVS algorithm for dense reconstruction. By automatically superimposing the 3D building and thermal point cloud models, 3D spatio-thermal models are formed, which enable the users to visualize, query, and analyze temperatures at the level of 3D points. The underlying algorithms for generating and visualizing the 3D spatio-thermal models and the 3D-registered digital and thermal images are presented in detail. The proposed method is validated for several interior and exterior locations of a typical residential building and an instructional facility. The experimental results show that inexpensive digital and thermal imagery can be converted into ubiquitous reporters of the actual energy performance of existing buildings. The proposed method expedites the modeling process and has the potential to be used as a rapid and robust building diagnostic tool.     

Optimization of functionally graded metallic foam insulation under transient heat transfer conditions

The problem of minimizing the maximum temperature of a structure insulated by a functionally graded metal foam insulation under transient heat conduction is studied. First, the performance of insulation designed for steady-state conditions is compared with uniform solidity insulation. It is found that the optimum steady-state insulation performs poorly under transient conditions. Then, the maximum structural temperature of a two-layer insulation with constant solidity for each layer is minimized by varying the solidity profile for a given total thickness and mass. It is found that the cooler inner layer of the optimal design has high solidity, while the hotter outer layer has low solidity. This is in contrast to the steady-state optimum, where the solidity profile is the reverse.     

不确定因素下建筑集群冷热电联供系统多目标优化

为降低建筑楼宇的能源消耗,研究建筑集群中的多个建筑楼宇共享冷热电联供系统、热能存储装置以及电池时的能源调度优化问题.考虑到建筑楼宇的能源需求和能源价格具有随机性,并且每个建筑楼宇以各自的费用最小化为目标,从随机规划和多目标的角度,建立建筑集群供能系统的两阶段多目标随机规划模型.为了提高模型的求解效率,提出将线性规划松弛与Benders分解算法相结合,从而获得建筑楼宇共享能源系统的Pareto最优解集.算例分析中通过CPLEX软件求解,对比分析不同随机因素对最优化建筑集群供能系统总费用以及建筑楼宇各自费用的影响程度,结果表明了所提出算法的有效性以及所构建的模型可以有效提高最优化决策的准确性.     

基于有限元模拟的薄膜热流计结构设计及优化

精确的热流测量对航空航天领域发动机设计及使用过程至关重要.薄膜热流计以其体积小、热容量小、干扰小、不破坏部件表面气流等显著优势,成为发动机热端部件表面热流测量的新方法.针对传统工程经验设计薄膜热流计精确度不高且迭代耗时长的缺点,基于有限元仿真模拟方法,建立了一种薄膜热流计有限元分析模型,综合分析了热流密度、热阻层厚度、热电堆厚度等因素对热流计冷热结点温度梯度的影响,提出薄膜热流计优化思路.分析结果表明,优化后的薄膜热流计具有更出色的热学性能与电学性能.     

Effects of slip on sheet-driven flow and heat transfer of a non-Newtonian fluid past a stretching sheet

The flow and heat transfer of an electrically conducting non-Newtonian fluid due to a stretching surface subject to partial slip is considered. The constitutive equation of the non-Newtonian fluid is modeled by that for a third grade fluid. The heat transfer analysis has been carried out for two heating processes, namely, (i) with prescribed surface temperature (PST-case) and (ii) prescribed surface heat flux (PHFcase) in presence of a uniform heat source or sink. Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective second order numerical scheme has been adopted to solve the obtained differential equations. The important finding in this communication is the combined effects of the partial slip, magnetic field, heat source (sink) parameter and the third grade fluid parameters on the velocity, skin friction coefficient and the temperature field. It is interesting to find that slip decreases the momentum boundary layer thickness and increases the thermal boundary layer thickness, whereas the third grade fluid parameter has an opposite effect on the thermal and velocity boundary layers.     

基于热舒适度的办公建筑HVAC系统节能控制

建筑节能控制是一个满足舒适需求条件下的多目标优化问题,然而对于缺失运行数据的新建建筑,如何控制供暖、通风和空调(HVAC)系统达到既舒适又节能的效果是一个控制难题.针对这个问题,本文首先建立了新建建筑空间模型,然后对该模型进行能耗仿真分析,在此基础上,提出基于人员热舒适度的模糊控制算法,得出最优控制区间,从而在较低能耗水平情况下获得更长的热舒适天数,达到既节能又舒适的目标.基于人员热舒适度的节能控制对建筑HVAC系统绿色运行具有促进作用.